During the second year of this project, we propose to specifically study transcutaneous electrical stimulation using high and low frequencies of less than 10 and 60 to 100. Patients who achieve good pain relief over several days will be given naloxone and a placebo to determine if reversal of the beneficial effect of TNS occurs. An additional 8 to 12 patients with dorsal column stimulators in place will be tested with naloxone according to the specific format already in use to amplify this aspect of the program. A few patients with peripheral nerve stimulators will also be tested.